The study of degradation of azo dyes using photochemical reaction and titanium dioxide

Abstract

Commercial samples of azo dyes: Saturn Yellow LFF 200, Saturn Red F3B 200 and Saturn Blue LBRR 200 (C.I. Direct Yellow 28, Direct Red 80 and Direct Blue 71) were purified and characterized by elemental analysis and mass spectroscopy. Dissolved dyestuffs have been photolysed in alkaline aqueous suspension (pH = 10) using polychromatic radiation of high pressure mercury lamp and titanium dioxide as a catalyst. The incident radiation (P = 1.21 x 10–4 Es.s–1.L–1) was measured by ferrioxalate actinometry in the range 200-600 nm. Active radiation for excitation of TiO2 (200-400 nm) was P0 = 4.2 x 10–5 Es.s–1.L–1. It was found that Saturn Yellow and Red fulfill the model of heterogeneous photocatalysis, while Saturn Blue decomposes even without catalyst. Kinetic model of heterogeneous photocatalysis was tested. The apparent efficiency of photodegradation (0.2-0.3%) as ratio of excitation rate and incident light was computed.